Main Battle Tanks and Armour Technology

[methos]

Read what I wrote above in post #2092. BM-42 has large caliber fins and an overall greater diameter -> this will lead to more friction/drag -> higher loss of velocity during flight. BM-42 has a fin diameter of 125 mm, while 120 mm APFSDS have allways less than 100 mm fin diameter.

Also as written in "Kampfpanzer Entwicklungen der Nachkriegszeit" monobloc penetrators have a higher penetration capability - DM 33 is monobloc, BM-42 uses a two-part tungsten core.

In my opinion the problem with WITU is that they base their "facts" probably at different sources. I.e. Jane's claims that DM 43 has a pressure value of 5500 bar (550 MPa), while U.S. sources attribute the same round with a chamber pressure of 5800 bar... because they probably use another base for their values. Rheinmetall stated in the old DM 63 article that DM 53/63 has a chamber pressure of 5500 bar at 15°c (the same as DM43). It has been claimed on German forums that at very hot climates (60-70°c) DM 53 is coming very close to the peak pressure of the shorter L/44 gun (7100 bar). So unless the Americans can't fire their APFSDS in hot climates (like Egypt, Afghanistan or Iraq) - which has been proven to be wrong - the U.S. use another base pressure values at least on a different situation (maybe also for velocity, but we don't know anything more detailed about it). So the 5800 bar for M829A2 in the image in post #2094 above could be practical 5500 bar at 15°c as for DM43.
One indicator that the U.S. might base their pressure values on another situation is the testing of KEW-A2 rounds in Leopard 2 tanks - there on page 14 is a graph about the performance of KEW-A2 regarding the dependency of speed on temperature: Jane's claimed that KEW-A2 has a muzzle velocity of 1,700 m/s - this is reached at ~22-23°c (~75°F) and not at 15°c! At 15°c the muzzle velocity is only ~1,675 m/s.

 

[methos]

double post

 

[militarysta]

[BTW:
Last but not least:
DM33A1 have penetrator diameter 28mm -during fly and in start of penetration process
3BM42 have penetrator "body" diameter 31mm -during fly but penetrator "rod" is only 22mm -and only this 22mm penetrate the target.
So in that parameter BM42 is better -of course DM33A1 is longer at 118mm, and finally have better penetration.

 

[militarysta]

Methos, I understand Yours poin of view, but my opinnion is slighty diffrent becouse IMHO dates or DM33A1 and BM42 are very very propably becouse:

3BM42 penetrator weight more (0,25kg) then DM33A1 -and we are talking about penetrator during fly...
3Bm42 have bigger (50m/s) muzzle velocity
During fly DM33A1 have 28mm diameter(penetrator), and Bm42 have 31mm max (penetrator) - propably Vdrop is simillar, but during penetration proces Dm33A1 have this 28mm still but in BM42 in penetration proces take ony dual "rod" of the penetrator whit diameter 22mm -so smaller then DM33A1.
Only one BIG advantage DM33A1 is 118mm longer penetrator, so with bigger rod(penetrator) diameter (disadvantage), and smaller penetrator weight (disadvantage) it can perforate more then 3BM42.

BTW: dual penetrator in BM42 is caused by penetratoin multi layers target capabilities.

 

[methos]

[BTW:
Last but not least:
DM33A1 have penetrator diameter 28mm -during fly and in start of penetration process
3BM42 have penetrator "body" diameter 31mm -during fly but penetrator "rod" is only 22mm -and only this 22mm penetrate the target.
So in that parameter BM42 is better -of course DM33A1 is longer at 118mm, and finally have better penetration.

We can't be really sure about the 22 mm diameter penetrator. Fofanov wrote that the diameter of the penetrator would be only 18 mm based on scale drawings.I did meassure the scale drawing from Russianarmour.org he put on his site and came up with an diameter of 28 mm, so I would assume that he made a typo. Nevertheless the real diameter is bigger, which means that some energy/penetrating power will be lost in the weaker steel.

3BM42 penetrator weight more (0,25kg) then DM33A1 -and we are talking about penetrator during fly...
3Bm42 have bigger (50m/s) muzzle velocity
During fly DM33A1 have 28mm diameter(penetrator), and Bm42 have 31mm max (penetrator) - propably Vdrop is simillar, but during penetration proces Dm33A1 have this 28mm still but in BM42 in penetration proces take ony dual "rod" of the penetrator whit diameter 22mm -so smaller then DM33A1.
Only one BIG advantage DM33A1 is 118mm longer penetrator, so with bigger rod(penetrator) diameter (disadvantage), and smaller penetrator weight (disadvantage) it can perforate more then 3BM42.

Well, do you know the penetrator weight? Mostly this also includes fins/cap(s) and in case of 3BM-42 steel jacket.
Vdrop of BM-42 is very likely higher due to the caliber fins. Fins are the main factor for vdrop.
Penetrator is probably bigger than 22 mm - at least it is in scale drawings (thus they might be incorrect).
The old DM 13 used also a two part penetrator - because monoblocs are harder to manufacture with a high L/D ratio, BM-42M has a monobloc penetrator. Two part penetrators are inferior.

________
Maybe relevant:
http://www.gd-ots.com/2011 Brochures/120mm KE-W.pdf
http://www.gd-ots.com/2011 Brochures/120mm KE-W A1 APFSDS-T.pdf
http://www.gd-ots.com/2011 Brochures/120mm KE-W A2 APFSDS-T.pdf
http://www.gd-ots.com/2011 Brochures/120mm IM HE-T.pdf

 

[militarysta]

from this:
Das Panzerdetail - die Munition der 125 mm Kanone D-81 (2A46, 2A46M, 2A75)
31mm during fly and if max is 31mm then when we rescale it give about ~18,6mm accoding draw.
On photo Vitalij Kuźmin 3BM42 rescaling give me about ~22 mm - so this 22mm are full possible.

Anyway -it's still less diameter then DM33A1 28mm.

 

[Godless-Kafir]

Methos, I understand Yours poin of view, but my opinnion is slighty diffrent becouse IMHO dates or DM33A1 and BM42 are very very propably becouse:

3BM42 penetrator weight more (0,25kg) then DM33A1 -and we are talking about penetrator during fly...
3Bm42 have bigger (50m/s) muzzle velocity
During fly DM33A1 have 28mm diameter(penetrator), and Bm42 have 31mm max (penetrator) - propably Vdrop is simillar, but during penetration proces Dm33A1 have this 28mm still but in BM42 in penetration proces take ony dual "rod" of the penetrator whit diameter 22mm -so smaller then DM33A1.
Only one BIG advantage DM33A1 is 118mm longer penetrator, so with bigger rod(penetrator) diameter (disadvantage), and smaller penetrator weight (disadvantage) it can perforate more then 3BM42.

BTW: dual penetrator in BM42 is caused by penetratoin multi layers target capabilities.

Did you mean it can not or can penetrate more?!! Either way 3mm difference is not such big deal.

 

[Damian]

Belive me, even these 3mm can make a difference between survival or death.

 

[Godless-Kafir]

Belive me, even these 3mm can make a difference between survival or death.

Either way, try saying this to the british and they are never going to accept it, as long as the Challenger had the rifled bore the Rifled bore was the best and everyone else was stupid and once they change to the Smooth bore the smooth bore is the best. Frankly i dont know how the challenger is good tank most of the time it is hiddeing behind the M1A.

Moreover in the future the KE penetrator only becomes smaller while the length gets longer. The metallurgy also improves so the diameter can be compromised for length.

 

[militarysta]

Did you mean it can not or can penetrate more?!! Either way 3mm difference is not such big deal.

No, no, no,
28 (Dm33A1) and 31mm (3Bm42) is during fly to the target - and in fact this 3mm is small, so Vdrp should be simmilar to the both penetrators.

But during penetration proces DM33A1 penetrator have still this 28mm but BM42 have more less - 22 or even 18mm, so the difrence is rather big = 6 or even 10mm... (rater 6mm).

Point of that all:

For that reson, despite the fact that DM33 have 118mm longer penetrator, ther is not so big difference in penetration values. Of course DM33A1 is better, but for mentioned reasons dates for both rounds can be very possible and DM33A1 is only about ~20mm better then BM42 in penetration values:
DM33A1 470mm (G) and ~520mm(A)
3BM42 450mm(G) and ~500mm(A)
(G) - guaranteed penetration
(A) - achievable penetration

And whole idea this all discusion is defending WITU dates -becouse in my opinnion they using guaranteed penetration dates, not achievable and that reason why many APFSDS have strangely undervalued dates, in fakt it should looks like this:
DM33A1 -470mm (G) to 520mm RHA (A)
DM43A1 - 560mm (G) to ~610mm RHA(A)
Polish 120mm -500mm(G) to ~550mm RHA (A)
etc.

And this difrence can explain why in one sources Dm53 for L-55 have 810mm RHA for 2000m and in other it have "only" 750mm for 2000 from the same gun (L-55).

 

[methos]

I did some more detailed measurements of the scale drawings on Kotsch's and Fofanov's pages. For the image on Fofanov's page the tungsten penetrator is about 25-26 mm (not including the blurred pixels) and about 28 mm when I include them. On Kotsch's page the scale drawing leads to an diameter of approximately 22 mm.
I googled and tried to found a real BM-42 and ended up with one which has a pretty unlucky angle, but it seems to lie between 22 and 25 mm, depending on how exactly is meassured. So the penetrator diameter seems to be less than the overall diameter of DM 33.

Still we should not forget that the diameter of BM-42 is in fact about 31-32 mm on the thinnest non-tip part. For an penetrator diameter of 22-26 mm some 30 to 50 % of the surface area are covered with steel. There a lot of energy will be lost, up to 25% of total, if a simple apporach by dividing densities and multiplying with percentages of surface area is correct.

Taking a look at images from the DM 33 round (like this with a lot of zoom or the images in the AMAP brochures) it seems quite possible that 28 mm refer to the thickest point of the projectile (the tip is thicker) and not to the average penetrator diameter. I don't want to speculate much more about this, but it may be somewhere about 24-26 mm average. Another point speaking against a diameter of 28 mm is the weight. 57 x 2.8 cm x 17.5 (density of typical 1980s WHA) => 6.1 kg!

To repeat myself again: The main reason for loss of velocity ("vdrop") is not the diameter of the sub-projectile containing the penetrator, but the size of the fins. DM 33 has fins with a diameter of about ~90 mm, while the fins of BM-42 are ~125 mm in diameter. The sub-projectile containing the penetrator has an ideal ballistic/aerodynamic shape, the fins not. Even though: a 28 mm diameter has a surface are of ~615 mm², while a 32 mm diameter has a surface area of ~804 mm². If the vdrop would only based on the diameter of the projectile body, then DM 33 would have a 23% lower vdrop.

BM-42 weighs less than DM 33 penetrator btw.

 

[militarysta]

I did some more detailed measurements of the scale drawings on Kotsch's and Fofanov's pages. For the image on Fofanov's page the tungsten penetrator is about 25-26 mm (not including the blurred pixels) and about 28 mm when I include them. On Kotsch's page the scale drawing leads to an diameter of approximately 22 mm.
I googled and tried to found a real BM-42 and ended up with one which has a pretty unlucky angle, but it seems to lie between 22 and 25 mm, depending on how exactly is meassured. So the penetrator diameter seems to be less than the overall diameter of DM 33.

When I mesured and rescaled it, its gives almoust 22mm diameter. I made it 6times for picture form Frontanow site, draws from Kotchs and this photo from Kuźmin (this in Your link) - all gives about 22mm.

Still we should not forget that the diameter of BM-42 is in fact about 31-32 mm on the thinnest non-tip part. For an penetrator diameter of 22-26 mm some 30 to 50 % of the surface area are covered with steel. There a lot of energy will be lost, up to 25% of total, if a simple apporach by dividing densities and multiplying with percentages of surface area is correct.

Propably not, becouse this designe was developed whit including this process - pleas look at BM42 tip (nose) it's not so simple.
According to Frontanow's site: The penetrators interfaced with the projectile body by means of a sheath manufactured of a low-melting-point alloy; during the penetration the sheath would melt allowing the penetrators to slide freely forward without losing energy and integrity on separation from the projectile body.
Yes I known - It's only posible not "divine truth" but...maybe it's like in this quotation and BM42 don't loose energy? Do You consider this possibility? (BTW: I never suppose that I will be defend russian weapons system - life is stange...)

Taking a look at images from the DM 33 round (like this with a lot of zoom or the images in the AMAP brochures) it seems quite possible that 28 mm refer to the thickest point of the projectile (the tip is thicker) and not to the average penetrator diameter. I don't want to speculate much more about this, but it may be somewhere about 24-26 mm average. Another point speaking against a diameter of 28 mm is the weight. 57 x 2.8 cm x 17.5 (density of typical 1980s WHA) => 6.1 kg!

Methos, DM-33A1 is well known in Poland - thousands of these rounds are in polish stocks and many of them where tested in Poland, in I really suppose that those dates are correct:
penetrator lenght: lengt 570mm, diameter 28mm, rod weight (during fly) 4,6kg But if mass in incorrect then how thick should be penetrator to have weight (whit fins...) 4,6kg? Maybe You have right and in fact DM-33A1 penerator is smaller then 28mm?

To repeat myself again: The main reason for loss of velocity ("vdrop") is not the diameter of the sub-projectile containing the penetrator, but the size of the fins. DM 33 has fins with a diameter of about ~90 mm, while the fins of BM-42 are ~125 mm in diameter. The sub-projectile containing the penetrator has an ideal ballistic/aerodynamic shape, the fins not.

Ok, You have convinced me

But it dosen't change problem that lighter penetrator whit bigger diameter doesn't be better then penetrator whit more weight and smaler diameter. In that cans DM33A1 is better becouse it have monolotick and longer penetrator...

BM-42 weighs less than DM 33 penetrator btw.

?? when?
BM-42 4,85kg (WITU, Frontanow)
DM-33A1 4,6kg (WITU)
?

 

[methos]

Yes I known - It's only posible not "divine truth" but...maybe it's like in this quotation and BM42 don't loose energy? Do You consider this possibility? (BTW: I never suppose that I will be defend russian weapons system - life is stange...)

I doubt that it is possible not to loose any energy. Kinetic energy is (following the old, conventional definition) 1/2 mass * velocity². A 2.8 kg penetrator (see below where this mass comes from) will therefore have a muzzle energy of about ~4 MJ, will the whole round (4.85 kg) will have a muzzle energy of about ~7 MJ. With sabot this figure rises to ~10 MJ. So there is plenty of energy stored inside the steel part and I doubt that the melting of the steel will increase the speed of the tungsten (physically impossible I would say).
Interessting is:
Area for 22 mm (pentrator): ~380 mm²
Area for 32 mm (penetrator + steel jacket): ~ 804 mm²
By dividing the area through the muzzle energy we can see that the penetrator only aspects shows better behavior:
~4000 kj / 380 mm² -> 10.5 kj per mm²
~7000 kj / 804 mm² -> 8.7 kj per mm²

Methos, DM-33A1 is well known in Poland - thousands of these rounds are in polish stocks and many of them where tested in Poland, in I really suppose that those dates are correct:
penetrator lenght: lengt 570mm, diameter 28mm, rod weight (during fly) 4,6kg But if mass in incorrect then how thick should be penetrator to have weight (whit fins...) 4,6kg? Maybe You have right and in fact DM-33A1 penerator is smaller then 28mm?

On DM 33/JM 33 (JM 33 = DM 33 licence made in Japan) the tip section is thicker than the rest of the penetrator. Afaik this is JM 33:

?? when?
BM-42 4,85kg (WITU, Frontanow)
DM-33A1 4,6kg (WITU)
?

A cylinder 22 x 420 mm will weigh ~2.8 kg with a typical tungsten alloy with a density of 17.5 g/cm³. A cylinder 28 x 570 mm will weigh ~6.1, with the diameter being 25 mm the weight decreases to ~4.9 kg... still to much for DM 33.
The problem now is: Do they mean the penetrator weight or the weight of the subcaliber projectile. For BM-42 it is the later one, but for DM 33 the first one seems to be more realistic, else we need to decrease even further, which would mean an even smaller averag diameter is required.

 

[methos]

Based on the KEW-A1 brochure:

More effective than a tungsten M829A1 (KEW) but less effective than a tungsten M829A2 (KEW-A2). Depending on the efficiency of DU 120 mm DM 43A1 might be better than M829A1.

 

[buttler]

militarysta
I am very eager to know the details of the polish scandal of reducing charge of dm-33a1.can you give me a source?or at least a polish military thread regarding it?

 

[Damian]

It was not a scandal.

Our military was performing ballistic tests of PT-91 armor against DM33A1, however in Europe there are not many proving grounds big enough to safely fire combat ammunition (belive me, APFSDS long rods can fly very far and it is dangerous to fire combat ammunition on proving grounds, especially smaller ones). So to simulate firing from specific distance, specialists from Bumar, taken some rounds and reduced propelant charge quantity in case, so round fired for example from 600m, will simulate target hit by projectile fired from 1600m.

Hope that this explains.

 

[W.G.Ewald]

It was not a scandal.

Our military was performing ballistic tests of PT-91 armor against DM33A1, however in Europe there are not many proving grounds big enough to safely fire combat ammunition (belive me, APFSDS long rods can fly very far and it is dangerous to fire combat ammunition on proving grounds, especially smaller ones). So to simulate firing from specific distance, specialists from Bumar, taken some rounds and reduced propelant charge quantity in case, so round fired for example from 600m, will simulate target hit by projectile fired from 1600m.

Hope that this explains.

Come on over to Fort Hood, Texas!

The Fort Hood Homepage

 

[Damian]

Guess what, in future I plans to travel to US if I be able to do that and gather materials for article or book even, about US Armor these days... damn, sit inside M1A2SEP v2, my small dream.

 

[W.G.Ewald]

Guess what, in future I plans to travel to US if I be able to do that and gather materials for article or book even, about US Armor these days... damn, sit inside M1A2SEP v2, my small dream.

Some armor links.

1st Armored Division (United States) - Wikipedia, the free encyclopedia

The United States Army | Fort Benning

Maneuver Center of Excellence Libraries

3rd Armored Division (United States) - Wikipedia, the free encyclopedia

"Hell On Wheels" Division Index Page

!st Cavalry Division is at Fort Hood.

North Carolina is the home of 252 Armor Regiment.

I was a member of C Co. (Armor) located in Southern Pines, North Carolina.

252nd Combined Arms Battalion - Wikipedia, the free encyclopedia

 

[methos]

Diehl has updated it's homepage. Amongst others there is a new AVePs APS flyer.